Latching secondary for two-stage carburetor



Nov. 24, 1959 L B, READ 2,914,052

LATCHING SECONDARY FOR TWO-STAGE CARBURETOR Filed June 25, 1956 3Sheets-Sheet 1 *INVENTOR.

LELAND B. READ /ad/zw ww ATTORNEY Nov. 24, 1959 1.. B. READ 2,914,052

7 LATCHING SECONDARY FOR TWO-STAGE CARBURETOR Filed June 25, 1956 sShets-Sheet 2 I IINVENTOR.

LELAND B. READ/ ATTORNEY. I

NOV. 24, 1959 READ 2,914,052

LATCHING SECONDARY FOR TWO-STAGE CARBURETOR File d June 25, 1956 sSheets-Sheet s INVENTOR. LELAND B. READ ATTORNEY United States Patent OLATCHING SECONDARY FOR TWO-STAGE CARBURETOR Leland B. Read, Normandy,Mo., assignor to ACF Industries, Incorporated, St. Louis, Mo., acorporation of New Jersey Application June 25, 1956, Serial No. 593,5196 Claims. 123-127) This invention relates to carburetors for internalcombustion engines, and more particularly to two-stage" carburetors ofthe type having one or more mechanically of this invention is to obtainpositive locking of the velocity operated secondary throttle orthrottles in closed position during idling and throughout part of therange of opening movement of the primary throttle or throttles, andmechanical release of the secondary throttle or throttles to permitopening thereof upon a predetermined opening of the primary throttle orthrottles, for example, upon opening of the latter to a degree withinthe range from twenty to thirty degrees before the wide-open primarythrottle position. This object is attained, according to the presentinvention, by providing latch means for locking the secondary throttleor throttles in closed position, and means movable with the primarythrottle or throttles for releasing the latch means upon a predeterminedopening of the primary throttle or throttles. A further feature of theinvention is the provision of means interconnecting the primary throttleor throttles and the secondary throttle or throttles for returning thelatter to closed position during the return of the former to closedposition. Other objects and features will be in part apparent and inpart pointed out hereinafter.

The invention accordingly comprises the constructions hereinafterdescribed, the scope of the invention being indicated in the followingclaims. I

In the accompanying drawings, in which one of various possibleembodiments of the invention is illustrated,

Fig. 1 is a view in elevation of one end of a four barrel carburetorembodying the invention, showing a secondary throttle latch and itsoperating means in the position assumed when the primary and secondarythrottles are closed;

Fig. 2 is a fragment of Fig 1 showing parts in the position assumed whenthe primary throttles are partly open, and immediately prior to releaseof the secondary throttles; I I I I I Fig. 3 is a view similar to Fig. 2showing the primary throttles moved somewhat beyond the position shownin Fig. 2, and showing the secondary throttles released and partly open;

Fig. 4 is a view in elevation of the other end of the carburetor,showing parts of a secondary throttle return mechanism in the positionassumed when the primary and secondary throttles are closed;

Fig. 5 is a vertical transverse section showing one primary mixtureconduit '(barrel) and the associated secondary mixture conduit (barrel)of the carburetor;

Fig. 6 is a view similar to Fig. 3 showing a further moved position ofparts corresponding to wide-open conditions of both the primary andsecondary throttles;

Fig. 7 is a fragment of Fig. 4 showing a moved position of parts assumedwhen the throttles are in the position corresponding to that shown inFig. 3;

Fig. 8 is a view similar to Fig. 7 showing a moved position of partsassumed when the throttles are in the position corresponding to thatshown in Fig. 2; and,

Fig. 9 is a view similar to Figs. 7 and 8 showing a moved position ofparts assumed when the throttles are in the position corresponding tothat shown in Fig. 6.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

Referring to the drawings, the invention is illustrated in itsapplication to a multi-barrel, multi-stage carburetor 1 of the typecommonly referred to as a four-barrel carburetor. Only so much of theconstruction of the carburetor as is essential to an understanding ofthis invention will be described herein. Reference may be made toCarlson et a1. U.S. Patent 2,715,522, dated August 16, 1955, forexample, for such further details as may be desired.

In general, the carburetor 1 comprises a fuel bowl section 3 having aflange 5 by which it may be attached to the intake manifold of theengine on which'the carburetor is used. Mounted on the fuel bowl 3 isthe usual air horn section 7. The'fuel bowl section 3 is formed toprovide two primary mixture conduits and two secondary mixture conduits.One primary mixture conduit, designated 9, and one secondary mixtureconduit, designated 11, appear in Fig.5. The air horn section 7 isprovided with a partition 13 dividing it to form a primary mixtureconduit inlet 15 and a secondary mixture conduit inlet 17.

A choke valve 19 is provided in the primary inlet 15 for controlling theadmission of air through the air horn section 7 to the two primarymixture conduits 9. The choke valve is fixed on a choke shaft 21 whichextends across the air horn section 7 from one end to the other abovethe primary mixture conduits (one of which is shown at 9 in Fig. 5).Each primary mixture conduit 9 has a main venturi 23 and a primaryventuri 25. As to each of the primary mixture conduits 9, a main fuelnozzle 27 opens into its primary venturi 25. It will be understood thatthe nozzles 27 are supplied with fuel from the fuel bowl section 3 in amanner such as that shown, for example, in U.S. Patent 2,715,522.

A primary throttle 29 is provided in each primary mixture conduit 9below the main venturi 23. The primary throttles for both conduits 9 ofthe four-barrel carburetor are fixed on a throttle shaft 31 whichextends across both these conduits. Adjacent one edge of each primarythrottle 29 are the usual idle ports 33 and 35 which are supplied withfuel via a passage indicated at 37. The port 35 is controlled by anadjustable needle valve 39 in known manner.

Each secondary mixture conduit 11 has a main venturi 41 and a primaryventuri 43. A fuel nozzle 45 opens into the primary venturi 43. This issupplied with fuel from the fuel bowl in a manner such as that shown,for example, in U.S. Patent 2,715,522. A secondary throttle 47 isprovided in each secondary mixture conduit 11 below the main venturi 41.The secondary throttles for both conduits 11 of the four-barrelcarburetor are fixed on a shaft 49 which extends across both theseconduits.

A choke mechanism housing is indicated at 51 (see Fig. 4). This containsa suction and temperature-responsive mechanism of the character shown inthe Coffey US. Patent 2,325,372. This mechanism includes a control armindicated at 53 connected by means of a link 55 to an arm 57 fixed onone end of the choke shaft 21 projecting out of air horn section 7.Fixed on the other end of the choke shaft 21 (at the other end of theair horn section 7) is an arm 59 (see Fig. 1). Arm 59 is connected bymeans of a link 61 to a fast idle cam lever 63 pivoted on the outside offuel bowl section 3 at 65.

Also pivoted at 65 is a latch 67. The lower edge of this latch is formedwith a shoulder 69 adapted for engagement by a dog 71 fixed on the endof the secondary throttle shaft 49 shown in Fig. 1. The latch 67 isbiased to rotate clockwise as viewed in Fig. 1 by a weight 73 at itsright end. Its left end is formed with a finger 75 adapted forengagement by an arm 77 formed integrally with a lever 79 fixed on theend of the primary throttle shaft 31 shown in Fig. 1 at the end of thelever 79 is an inturned lug 81 adapted to engage the fast idle cam lever63 when the primary throttles 29 are fully opened, so as partially toopen the choke valve 19 for unloading purposes. The primary throttleshaft 31 also carries an actuating lever 83 provided with a hole 85 forconnection of an actuating rod (not shown). A lug 87 on the lever 83 hasan idle set screw 89 threaded therein for adjusting the closed positionof the primary throttles 29. Lever 83 is connected by a link 91 to oneend of a pivoted lever 93 adapted to operate the plunger 95 of anaccelerating pump (not shown).

An arm 97 is fixed on the end of the primary throttle shaft 31projecting out of the end of the fuel bowl section 3 at which thehousing 51 is located (see Fig. 4). An arm 99 is rotatable on the end ofthe secondary throttle shaft 49 shown in Fig. 4. A link 101 has one endpin-connected to arm 97 at 103 and its other end 105 received in a slot107 in arm 99. This provides a lost-motion connection between arms 97and 99. An edge portion of the arm 99, indicated at 109, is arranged inabutting relation with an inturned lug 111 on an arm 113 secured to thesecondary throttle shaft 49. Arm 113 carries a weight 115 for biasingthe secondary throttles 47 closed. The secondary throttles are velocityoperated, i.e., unbalanced to open against the closing bias of theweight 115 in response to suction in the secondary mixture conduits 11-posterior to the secondary throttles. A cam 117 on the arm 97 isengageable with a cam follower 119 on the arm 99 for assisting thereturn of the secondary throttles to closed position as will appear.

Operation is as follows:

The choke valve 19, the primary throttles 29 and the secondary throttles47 are shown closed in Figs. 1, 4 and 5. The secondary throttles 47 arelocked against opening by engagement of the dog 71 with the shoulder 69of latch 67 (see Fig. 1). The arm 99 occupies a position between the lug111 on arm 113 and the cam 117 on arm 97 (see Fig. 4). The end 105 oflink 101 is located at the right end of the slot 107 in arm 99, asviewed in Fig. 4.

To open the primary throttles 29, the lever 83 is swung clockwise asviewed in Fig. 1 by the actuating rod (not shown). This rotates theprimary throttle shaft 31, lever 79 and the primary throttles 29clockwise as viewed in Fig. 1, and rotates the arm 97 counterclockwiseas viewed in Fig. 4. The latch 67 remains in the Fig. 1 lockingposition, holding the secondary throttles 47 against opening, until thearm 77 on lever 79 engages the finger 75 on the latch and rotates thelatch counterclockwise as viewed in Fig. 1 far enough for the dog 71 toescape from the shoulder 69. Fig. 2 shows the arm 77 in the positionwhere it first comes into engagement with finger 75, and Fig. 3 showsthe arm 77 rotated a few degrees past the Fig. 2 position to a positionwhere it has raised the latch 67 sufficiently to release the secondarythrottles. This release position is preferably within the range fromtwenty degrees to thirty degrees ahead of the wide-open position of theprimary throttles, the latter being shown in the wide-open position inFig. 6. 9

Upon the stated counterclockwise rotation of the arm 97, the cam 117 onthis arm moves downward past the follower 119 on the arm 99, and the endof link 101 slides from the right end of the slot 107 in arm 99 to theleft end of the slot (compare Figs. 4 and 8). The cam 117 clears thefollower 119 somewhat prior to release of the latch 67. Uponcounterclockwise rotation of the arm 97 past the Fig. 8 position, thelink 101 is dragged to the right as viewed in Fig. 8, thereby freeingthe arm 99 for clockwise rotation. This frees the secondary throttles 47for opening against the bias of weight in response to suction. However,even if the secondary throttles do not open under suction, arm 97 maycontinue to rotate counterclockwise upon opening of the primarythrottles past the Fig. 8 position due to the lost motion of the end 105of the link 101 in slot 107 and the capability of arm 99 to rotaterelative to the secondary throttle shaft. Assuming that the secondarythrottles do open, the degree of opening is controlled by the primarythrottles because of the engagement of the lug 111 on arm 113 with theedge portion 109 of arm 99, and the engagement of the left end of theslot 107 with the end 105 of link 101.

Assuming that the primary throttles 29 are moved to the wide-openposition and that the secondary throttles 47 have been moved by suctionto their wide-open position, the parts will occupy the position shown inFigs. 6 and 9. Upon return of the primary throttles to the closedposition, lever 79 rotates counterclockwise as viewed in Fig. 6 and arm97 rotates clockwise as viewed in Fig. 9. Arm 97 acts through engagementof the cam 117 with the follower 119 on arm 99 and through the link 101to rotate the arm 99 counterclockwise, and arm 99 acts throughengagement of its edge portion 109 with lug 111 on arm 113 to return thesecondary throttles to closed position. Closure of the secondarythrottles occurs when the arm 97, returning clockwise from the positionshown in Fig. 9, reaches the position shown in Fig. 8. At this point,the dog 71, returning clockwise from the position shown in Fig. 6,reaches the position shown in Fig. 2. Lever 79, returningcounter-clockwise from the position shown in Fig. 6, reaches theposition shown in Fig. 2 and the finger 75 on the latch 67 is releasedfrom the arm 77 on lever 79 so that the latch drops into lockingposition with respect to the dog 71, thereby locking the secondarythrottles against opening.

From the above description, it will be apparent that the velocityoperated secondary throttles 47 of the carburetor are positively lockedagainst opening in response to development of suction in the secondarymixture conduits 11 posterior to throttles 47 during idling (primarythrottles in closed position) and throughout the part of the range ofopening movement of the primary throttles from the closed position shownin Fig. 1 to the partly open position shown in Fig. 3. At this point,the secondary throttles are released for opening under suction againstthe closing bias of the weight 115. The degree of their opening afterrelease depends upon the position of the primary throttles. They arereturned to closed position and locked in closed position imme diatelyupon the return of the primary throttles to closed position.

While the invention is herein illustrated as it pertains to afour-barrel carburetor, it will be understood that its principles areequally applicable to a two-barrel carburetor (one primary barrel andone secondary barrel).

In view of the above, it will be seen that the several objects of theinvention are achieved and other advansequ res ts attaine lvention, itis intended that all matter contained in the above description or shownin the accompanying drawings shall be interpreted as illustrative andnot in a limiting sense.

I claim:

1. In a carburetor having a primary throttle and a secondary throttle,rigid means for locking the secondary throttle in closed position duringinitial opening move ment of said primary throttle comprising a movablelatch biased toward locking position and movable away from lockingposition against the bias for releasing the secondary throttle, andmeans movable with the primary throttle and engageable with said, latchfor moving it away from locking position upon a predetermined opening ofthe primary throttle.

2. In a carburetor having a primary throttle on a primary throttle shaftand a secondary throttle on a secondary throttle shaft, rigid means forlocking the secondary throttle in closed position when the primarythrottle is closed and throughout part of the range of opening movementof the primary throttle comprising a movable latch biased toward lockingposition and movable away from locking position against the bias, amember on the secondary throttle shaft engageable with the latch whenthe latch is in locking position to hold the secondary throttle closed,and a member on the primary throttle shaft engageable with the latch tomove it away from locking position upon a predetermined opening of theprimary throttle.

3. In a carburetor having a primary throttle and a velocity operatedsecondary throttle, rigid latch means for locking the secondary throttlein closed position during initial opening movement of said primarythrottle, means movable with the primary throttle for releasing thelatch means to allow the secondary throttle to open upon a predeterminedopening of the primary throttle, and means interconnecting the primaryand secondary throttles for returning the secondary throttle to closedposition upon return of the primary throttle toward closed position.

4. In a carburetor having a primary throttle and a velocity operatedsecondary throttle, rigid means for locking the secondary throttle inclosed position during initial opening movement of said primary throttlecomprising a movable latch biased toward locking position and movableaway from locking position against the bias for releasing the secondarythrottle, means movable with the primary throttle and engageable withsaid latch for moving it away from locking position to allow thesecondary throttle to open upon a predeterminad opening of the primarythrottle, and means interconnecting the primary and secondary throttlesfor returning the secondary throttle to closed position upon return ofthe primary throttle toward closed position, said latch-engaging meansthereupon releasing said latch to allow it to return to locking positionunder its bias.

5. In a carburetor having a primary throttle on a primary throttle shaftand a velocity operated secondary throttle on a secondary throttleshaft, nonyielding means for locking the secondary throttle in closedposition when the primary throttle is closed and throughout part of therange of opening movement of the primary throttle comprising .a movablelatch biased toward locking position and movable away from lockingposition against the bias, a member on the secondary throttle shaftengageable with the latch when the latch is in locking position to holdthe secondary throttle closed, a member on the primary throttle shaftengageable with the latch to move it away from locking position to allowthe secondary throttle to open upon a predetermined opening of theprimary throttle, and lost-motion means interconnecting the primary andsecondary throttles for returning the secondary throttle to closedposition upon return of the primary throttle toward closed position,said member on the primary throttle shaft thereupon releasing said latchto allow it to return to locking position under its bias.

6. In combination with an internal combustion engine having primary andsecondary induction systems, primary and secondary throttles,respectively, in said conduits, said secondary throttle beingautomatically opened in response to operation of the engine above apredetermined capacity, rigid means to latch said secondary throttleclosed when the engine is operating below said capacity, and means torelease said latch means responsive to a condition incident to operationof the engine substantially at said capacity, said secondary throttlebeing unbalanced to open.

References Cited in the file of this patent UNITED STATES PATENTS2,420,925 Wirth May 20, 1947 2,609,187 S..ott Sept. 2, 1952 2,752,133Egerer June 26, 1956

